Field
The present disclosure relates to an aerosol-generating article comprising a hydrochromic material, an aerosol-generating system comprising the aerosol-generating article, and an aerosol-generating device comprising an electronic photosensor.
Description of Related Art
One type of aerosol-generating system is an electronic cigarette. Electronic cigarettes typically use a liquid aerosol-forming substrate which is vaporised to form an aerosol. An electronic cigarette typically comprises a power supply, a liquid storage portion for holding a supply of the liquid aerosol-forming substrate, and an atomiser.
The liquid aerosol-forming substrate needs to be replenished when depleted. The most common way to supply refills of liquid aerosol-forming substrate is in a cartomiser-type cartridge. The cartomiser may be regarded as a consumable aerosol-generating article, and the reusable part of the electronic cigarette may be regarded as an aerosol-generating device. A cartomiser may comprise both a supply of liquid substrate and the atomiser, usually in the form of an electrically-operated resistance heater wound around a capillary material soaked in the aerosol-forming substrate. Replacing a cartomiser as a single consumable unit avoids the need to clean or otherwise maintain the atomiser. However, it may be difficult to determine when the liquid aerosol-forming substrate in a cartomiser has been exhausted. Therefore, it may be difficult to determine when to replace a consumable part of an aerosol-generating system, such as the cartomiser of an electronic cigarette.